First time I hear of "Combustible". No idea what is going wrong, but since our server works with any client I have tried otherwise, I would assume the error is on their side. Most likely they have not yet updated to the latest Lemmy API version.

We host a nice mobile client here by the way: https://voyager.slrpnk.net/

Try Eternity. It's FOSS, repository is on Codeberg.

I've been using Thunder. It's honestly been pretty good.

I also keep Voyager as a backup in case Thunder ever disappears. It also comes as a PWA if that's your thing.